This invention relates generally to high-power solid-state lasers and, more particularly, to systems for producing laser beams of extremely high brightness. Solid-state lasers with an average power up to 100 W (watts), and even higher powers, are needed in a variety of military, industrial and commercial applications, including X-ray photolithography, laser machining and drilling, space and underwater communication, and medical applications.
The brightness of a laser beam is proportional to the average power and is inversely proportional to the square of the beam quality, where the beam quality is in turn defined in relation to a diffraction-limited beam, i.e., a diffraction-limited beam has an ideal beam quality of 1.0. A worse beam quality of, say, 1.5 results in a brightness of 1/(1.5).sup.2 or 44.4% of the brightness of the diffraction limited beam. Since the brightness falls off in proportion to the square of the beam quality, it is extremely important to control the beam quality if high brightness is a design goal.
A number of laser architectures disclosed in various prior patents use a phase conjugated master oscillator power amplifier (PC MOPA) configuration, but still fail to produce a desirably bright beam, or have other drawbacks. Accordingly, there is still a significant need for an improved solid-state laser architecture providing excellent beam quality and, therefore, an extremely bright beam. The present invention satisfies this need, as outlined in the following summary.